The Global System for Mobile Communications (GSM) standard was developed as a replacement for first generation (1G) analogue cellular networks, and originally described a digital, circuit-switched network optimized for full duplex voice telephony. This was expanded over time to include data communications, first by circuit-switched transport, then packet data transport via General Packet Radio Services (GPRS) and Enhanced Data rates for GSM Evolution (EDGE) (or EGPRS).
Subsequently, the 3rd Generation Partnership Project (3GPP) developed 3rd Generation Wireless Mobile Communication Technology (3G) Universal Mobile Telecommunications System (UMTS) standards followed by fourth generation (4G) Long Time Evolution (LTE) Advanced standards.
The Universal Terrestrial Radio Access Network (UTRAN) is a collective term for the base stations, or Node B's, and Radio Network Controllers (RNCs) which make up the UMTS radio access network. This communications network, commonly referred to as 3G, can carry many traffic types from real-time Circuit Switched (CS) to IP based Packet Switched (PS). The UTRAN allows connectivity between the UE (user equipment) and the core network (CN).
The UTRAN contains the base stations, or Node Bs, and Radio Network Controllers (RNC). The RNC provides control functionalities for one or more Node Bs. The RNC and its corresponding Node Bs make up the Radio Network Subsystem (RNS). There can be more than one RNS present in a UTRAN.
There are four interfaces connecting the UTRAN internally or externally to other functional entities: Iu, Uu, Iub and Iur, see FIG. 1. The Iub is an internal interface connecting the RNC with the Node B. Also, there is the Iur interface which is an internal interface most of the time, but can, exceptionally, also be an external interface for some network architectures. The Iur connects two RNCs with each other.
The Uu interface is an external interface connecting the Node B with the User Equipment (UE). The Iu interface is also external and connects the RNC to the Core Network (CN). The IuCS interface in FIG. 1 carries the CS traffic types and the IuPS interface carries the PS traffic types. The Iu interface in 3G corresponds to the A interface between the Mobile Switching Center (MSC) and the Base Station Controller (BSC) in GSM.
Across the Iu interface, the Iu general control services and the Iu notification services are implemented. The general control services are services related to the whole Iu interface instance between the RNC and CN. For instance, the Reset procedure used to initialize the UTRAN in the event of a failure in the CN or vice versa, is one of the procedures used to implement the general control services.
The Radio Access Network Application Part (RANAP) protocol is used in UMTS for signalling between the CN and the UTRAN over the Iu interface. The RANAP signalling protocol resides in the control plane of the Radio network layer of the Iu interface in the UMTS protocol stack.
In the event of a failure at the UTRAN which has resulted in the loss of transaction reference information, a RANAP RESET message is sent to the CN. This message is used by the CN to release affected Radio Access Bearers and erase all affected references. After a guard period a RESET ACKNOWLEDGE message is returned to the UTRAN indicating that all references have been cleared.
Correspondingly, in the event of a failure at the CN which has resulted in the loss of transaction reference information, a RANAP RESET message is sent to the RNC. This message is used by the UTRAN to release affected Radio Access Bearers and erase all affected references. After a guard period a RESET ACKNOWLEDGE message is returned to the CN, indicating that all Ues which were involved in a call are no longer transmitting and that all references at the UTRAN have been cleared.
Resources related to a specific UE in UTRAN and CN are controlled over the Iu interface by utilising the Iu signalling connection. In case this signalling connection is abnormally released, there has to be a mechanism to reset the resources that were previously controlled by the abnormally released Iu signalling connection.
One possible way to realise this functionality is to rely on indication from the Iu signalling connection itself, which would tell the user of the signalling connection that an error having resulted to an abnormal release of the signalling connection has occurred.
To maintain the independency between transport and radio network layers an explicit RANAP procedure Reset Resource has been introduced. The purpose of the Reset Resource procedure is to restore the information in CN/UTRAN in the case of a failure which has affected only a small part of the equipment (e.g. abnormal Iu signalling connection release, or resource hanging).
If a resource has to be put to idle at the UTRAN due to an abnormal Iu signalling connection release, a RESET RESOURCE message shall be sent to CN. When CN receives this message, it clears all the resources (if any) used for the indicated resources to be reset and returns RESET RESOURCE ACKNOWLEDGE message to UTRAN.
Correspondingly, if a resource has to be put to idle at CN due to an abnormal release of Iu signalling connection, a RESET RESOURCE message will be sent to the UTRAN. When RNC receives a RESET RESOURCE message, it shall respond with a RESET RESOURCE ACKNOWLEDGE message and release all UTRAN resources (if any) associated to the indicated resource to be reset.
Thanks to the development of the Universal Terrestrial Radio Access Network (UTRAN) system, the RNC has become more and more scalable. The mega RNC has been developed to manage large metropolitan Universal Mobile Telecommunications System (UMTS) networks so the capacity of the RNC in terms of number of connected User Equipment (UEs) has been increased dramatically.
Since the networks have evolved to handle more and more users, the current procedures for resetting network resources encounter capacity problems, for example message congestion and/or latency in the reset procedures. The problems are not limited to 3G, but are also present in other wireless networks, such as for example GSM.
Thus, there is a general need of a more efficient procedure for resetting network resources in wireless networks.